Century Egg (Pidan)

What it is

A duck (or chicken/quail) egg preserved by alkaline curing until the white turns to a translucent amber-brown jelly and the yolk to a creamy, dark green-gray center. Also called "thousand-year egg" — though it takes weeks, not centuries.

How it's made (the chemistry) — Eggs are coated and packed in an alkaline mixture of clay, wood ash, quicklime (calcium oxide), salt, and rice hulls (or soaked in a lye/tea brine) for weeks to a few months. The high pH denatures the proteins without heat (a chemical "cooking"), raising the egg's pH dramatically: the white sets into clear jelly, and the yolk develops its dark color and creamy texture along with sulfur and ammonia compounds. The lacy "pine-flower" (songhua) crystal patterns sometimes seen in the white are amino-acid crystallizations.

Flavor profile

Rich, creamy, intensely savory and sulfurous, with an ammoniacal edge; the yolk is custardy and complex, the white mild and jelly-like.

Culinary uses

Sliced over congee (century egg & pork congee), with chilled tofu (pidan tofu) and soy-sesame dressing, with pickled ginger, and in Hunanese stir-fries.

Regional variations

Some are made firmer or softer; quail-egg pidan are bite-sized; brine methods now often replace the traditional lime-clay pack for safety and consistency.

Cultural & historical context

A centuries-old Chinese preservation craft and one of the most misunderstood foods in the Western imagination, where its appearance and aroma read as "rotten" despite being a controlled chemical cure.

Reference notes

Tags: `egg`, `alkaline-cured`, `preserved`, `chinese`. Related: salted duck egg, sufu. Cuisine: Chinese. Links → Congee, Pidan Tofu, Alkaline Preservation.